Diving Bottom Stages Pros/Cons

[rjack321]

I wouldn't start with near empty doubles. Fill them and the stage, then just breathe the stage for dive 1 and if there's a dive 2 breathe the doubles. If there's no dive 2 take them home full and use them another day. If the dive is a little deeper or longer or whatever you'll appreciate having more than 100bar in your twins.
Oh and I would start on the stage and stay on it until its empty. The biggest risk here is accidentally starting the dive on your deco gas. Be absolutely sure you and your buddy check which reg you are breathing on at the surface, which can be a chaotic time jumping in on a time schedule etc.

 

[GrimSleeper]

Yes, but I want a standard gas

Fair enough.

That one is a bit of a myth.

Not with any twins I've ever had - I don't mean teeny tiny Helium leaking out and leaving Oxygen and Nitrogen behind, I just mean leaking! I seem to spend half my life breaking down my twinsets to fix small but annoying neck leaks.

Not sure why everyone keeps thinking I have three stages. It would just be bottom stage and 50%

Assumed for 44m dive it was just bottom gas and 50%. Was responding to KevRumbo, but couldn't be bothered with fancy quote thingies...

 

[rjack321]

Not with any twins I've ever had - I don't mean teeny tiny Helium leaking out and leaving Oxygen and Nitrogen behind, I just mean leaking! I seem to spend half my life breaking down my twinsets to fix small but annoying neck leaks.

Are these ali cylinders? Resurface the neck sealing surfaces, PSI sells a tool for this.

 

[Kevrumbo]

It was my training that, if you are using a bottom stage, you start on it, because it's your most fragile gas source (not firmly attached to you, only one regulator).

I was also trained never to put bottles down on an OW or penetration dive, because you can never be sure you will get back to them.

. . . .
I know conventional wisdom says you should be scootering if you have three slung stages, but I've swum twinned 80s and three slung 80s without it significantly increasing my SCR or giving me CO2 problems. Course, I don't as a rule swim very fast...

In one more week, I will be on double 11L Cylinders (AL80's), slung 50% and O2 deco bottles and a 11L stage tank at over 45m deep diving on the 888'/280m long Aircraft Carrier USS Saratoga in Bikini Atoll: and I will definitely be using a scooter my entire ten day expedition out there. The hanger deck is so large & cavernous that I might not need to drop any bottles off in order to penetrate.

Conversely, on something small like the I-169 Sub at 30m in Truk (where I'll be in three weeks right after Bikini) , you do need to drop your O2 bottle and leave it outside if you want to go inside the tight confines of the pressure hull. (And I'll be on Z sidemount as well).

Never say never Lynne --ad lib, pro re nata . . . but obviously you better make sure you can find those deco/stages again if you must drop then.

The best thing about this trip is that I can refill my gases after every dive, so the problem of the OP is not an issue for me. . .

 

[GrimSleeper]

Are these ali cylinders? Resurface the neck sealing surfaces, PSI sells a tool for this.

You don't have a link, do you? Googling is a bit of a random exercise out here in the middle of nowhere, although I did find something that'll fit the bill. Never occurred to me you could buy such a thing. Just goes to show, you don't know what you don't know...

 

[JamesK]

You don't have a link, do you? Googling is a bit of a random exercise out here in the middle of nowhere, although I did find something that'll fit the bill. Never occurred to me you could buy such a thing. Just goes to show, you don't know what you don't know...

here is a brochure about it, complete with contact info.
http://www.visualplus.net/oringer/oringerbrochure.pdf


check out www.visualplus.net for more info

 

[Ste Wart]

Tried out the bottom stage last night. I'd forgotten what its like to dive with two stages, a lot of my diving has been single cylinder deco of late. The 11L and the 7L weren't uncomfortable, but they were noticeable. Especially on the deco, when the very empty (20bar) 11l was floaty and affected the whole deco rather than a gradual increase in buoyancy over the course of the deco. Next week will be stage work to tidy up a few things as I wasn't particularly happy with the ascent.

That said the gas bill was much easier to deal with and diving the bottom stage will preserving the back gas is a good way to eek out the backgas over two or more dives